Abstract
This study analyses the seasonal distribution in the superficial sediments of the Marchica watershed of trace and major elements, grain size, and total organic carbon. Samples were taken during the wet and dry seasons of 2018 in the mainstream valleys carrying the discharges to the Marchica Lagoon. Ecotoxicological indices (Enrichment Factor, Contamination Factor, Pollution-Load Index) and sedimen-quality guidelines were used to evaluate the ecotoxicological risk. The results revealed during both wet and dry seasons contamination by lead in all stream valleys. The northwest stream valley, characterized by some industrial activities, and the stream valley crossing the abandoned mine were the most polluted by zinc and copper. Minimal pollution for Cr, Co, and Ba was found during both the wet and dry seasons. Despite the restoration actions achieved around the Ramsar site of Marchica lagoon during the last decades, the watershed continues to have a negative impact on this ecosystem. Therefore, an environmental management strategy isnecessary, taking into account the rehabilitation of the abandoned mining sites, the rational use of pesticides and fertilizers in agriculture, and the environmental responsibility of industrial companies, especially those installed before the implementation of the national law on environmental impact studies.
Highlights
Watersheds surrounding the coastal lagoons have experienced intense urbanization in recent years due to the ecosystem services offered by these ecosystems
This study analyses the seasonal distribution in the superficial sediments of the Marchica watershed of trace and major elements, grain size, and total organic carbon
An environmental management strategy is necessary, taking into account the rehabilitation of the abandoned mining sites, the rational use of pesticides and fertilizers in agriculture, and the environmental responsibility of industrial companies, especially those installed before the implementation of the national law on environmental impact studies
Summary
Watersheds surrounding the coastal lagoons have experienced intense urbanization in recent years due to the ecosystem services offered by these ecosystems. This urbanization accompanied by the intensification of human activities around coastal lagoons has impacted their structure and function and compromised their ecological integrity [1,2]. Sediment flows in rivers reflect natural or human-induced changes in their watersheds [3]. The Marchica watershed constitutes an example with a population of approximately 400 000 from cities around the Ramsar site of the Marchica lagoon. The watershed covers an area of 700 km and is formed by four morphological structures, the volcanic massif of Gourougou in the northwest, the massif of Beni BouIffrour in the west; the Kebdana massif in the south; and the Bouarg plain in the southwest [5, 6]
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